1. Field of the Invention
This invention is related to reading and processing machine readable information on an item, and, more particularly, to a process for verifying the identity of the article by determining that machine readable information, such as a barcode pattern, read on an item matches the item.
2. Summary of the Background Art
The patent literature includes a number of descriptions of methods for a self-check-out process using a physical feature of an article being purchased to verify the identity of the article after machine readable information on the article has been scanned. Such a method is used to guard against attempts at deception, such as placing a barcode label from a less expensive item on the article being purchased or scanning one item before sending another item to be placed in a shopping bag.
For example, U.S. Pat. No. 4,792,018 describes such a system including a code reader for generating an output signal indicating a distinct code identifying an article, a conveyer for receiving and transporting the article, an entrance sentry for defining an inlet to a secured zone extending along a portion of the conveyor and for generating an output signal indicating the entry of the article into the secured zone and further indicating a measurable characteristic of the article, and a controller for moving the conveyor to accept or reject the article. The sentry may include a number of light beams forming a light curtain extending upward from the conveyor and across the conveyer at the inlet to the secure area, and a number of photocells receiving the individual light beams, with the number of beams broken by the movement of the article through the inlet indicating its height over the conveyor.
U.S. Pat. No. 5,609,223 describes another such system in which image obtaining means, such as a video camera looking downward on the article is placed near the light curtain. The article may be rejected based on physical features of the article included in the article image obtained by the image obtaining means. Alternatively, the height of the article may be measured by projecting a slit pattern of light at the top of the article, and by measuring the displacement, from the axis of the video camera lens, of the line at which the light strikes the top of the object. Along with the measurement of the height of the article, the position and shape of the article can be detected based on the two-dimensional image of the slit light as the article passes under the video camera. In another method, the height of the article is measured by evaluating the reflection of an ultrasonic wave directed downward toward the object.
What is needed is a reliable method for determining the orientation of the article when its height or other physical characteristic is measured. An article may differ greatly in its three dimensions, so that a measurement of a single dimension is not sufficient for identifying the article. Additionally, what is needed is a means for determining a dimension of an article as it is scanned, when the relationship between the machine readable information and the dimension is known.
The stationary barcode scanners typically used today for checking out articles being purchased are typically omnidirectional optical scanners in which a laser beam is deflected by a multifaceted spinning mirror and by a number of stationary mirrors disposed at various angles to form a number of scan lines projected through a window into a space adjacent the scanner. Within this space, the scan lines are laterally displaced from one another and are additionally disposed to extend at several different angles, in an arrangement making the placement and orientation of the barcode being scanned non-critical, so that many different types of articles can be scanned quickly and easily. Descriptions of such omnidirectional optical scanners found, for example in U.S. Pat. Nos. 3,947,816, 4,713,532, 5,216,232, 5,557,093, 5,637,852, and 6,098,885.
What is needed is a method for determining which of the various scan lines from the omnidirectional scanner is successfully used to read machine readable information and for subsequently determining a range of possible locations for the barcode and for other visible features on the article being scanned as it is scanned.
A number of other patents describe apparatus and methods for reading machine readable informations from the output of a video camera. For example, U.S. Pat. No. 5,155,343 describes a bar code reader including an optical system for storing in memory a two-dimensional image containing a bar code symbol. The location of the bar code image is detected by computing the accumulated sum of the products of the derivatives of respective first and second scan lines as a location score for the image under consideration. The higher the location score, the higher the probability that the area under consideration contains a bar code image. Also, a method and apparatus is disclosed for determining the fine orientation of a located bar code image by the crosscorrelation of interpolated scan line data. The bar code image is filtered by shifting interpolated scan line data in accordance with the detected peak of the cross-correlation and combining the shifted scan line data.
U.S. Pat. No. 5,155,343 describes an omnidirectional bar code reader using a virtual scan of raster scan digital image memory to create the equivalent scanning pattern of a mechanical laser scanner. A two dimensional image of bar code symbol at any random orientation is captured in a memory. In one embodiment, the image memory is scanned to create a virtual scan equivalent to the scan pattern of a laser scanner. In another embodiment, the image memory is divided into plurality of memory segments, and simultaneous virtual scan is provided in each of the respective memory segments. In yet another embodiment, the memory is divided into a plurality of overlapping memory segments and simultaneous virtual scan is provided in each of the respective overlapping memory segments. The overlap between the memory segments is made large enough so that a bar code symbol of the expected size will be entirely included in one or the other of the overlapping memory segments. Thus, the boundary problem between memory segments is resolved and it is not necessary to concatenate partial scans between adjacent memory segments. The segmented scan may be achieved using an interleaved memory storage arrangement.
U.S. Pat. No. 6,135,354 describes a barcode image processing system which processes video signals including video data representing images of barcode labels to be decoded and verified. A video signal containing video data representative of successive images of a plurality of barcode labels is processed to extract the video data and the horizontal and vertical synchronization signals from the video signal. A digitalization circuit is provided which digitalizes the video signal over a varied threshold voltage. The range or deviation of the threshold voltage which yields decodable video data is used as a measure of a quality of a barcode label. A gate trigger signal is generated which is synchronized to the vertical synchronization signal and which controls when a barcode decoder decodes video data for a horizontal line taken from a barcode image. A masking circuit is provided to mask out portions of a video field except for a portion sufficient to contain one barcode label, which is useful in the situation where barcode labels are printed very close together.
U.S. Pat. No. 6,698,833 describes a system including omnidirectional barcode locator that processes, in realtime, a digital video signal defining a pixelized image of a conveyor carrying parcels through the field of view of a CCD camera. The omnidirectional barcode locator divides the video image into a plurality of cells and produces two output signals, a cell barcode indication signal and a cell barcode orientation signal, for each cell. A host computer responds to a “true” cell barcode indication signal for a cell by storing the portion of the video image corresponding to the cell in a mass storage memory. 7be host computer also stores a representation of the cell barcode orientation signal for each cell in which the cell barcode indication signal is “true.” The omnidirectional barcode locator thus allows the host computer to store only those cells of the video image that contain barcode data. The barcode data may then be provided to a barcode reader for further processing.
Other patents describe the use of images from multiple video cameras to determine the location of features of an object in three-dimensional space. For example, U.S. Pat. No. 4,654,872 describes a system for recognizing a three-dimensional object includes a plurality of image pickup apparatus, e.g. television cameras, by which images of the object are picked up from at least three directions. Feature points are extracted from each of at least three images obtained. Two sets of feature points on epipolar lines are formed, with the lines being formed on at least two of the images by a feature point on another image. A set of feature points is selected to satisfy a restricting condition determined by the relationship of the image pickingup direction.
U.S. Pat. No. 6,445,814 describes three-dimensional information processing apparatus for obtaining three-dimensional information from an object having a three-dimensional shape, and performing predetermined information processing, comprises: a camera for sensing images of the object from a plurality of coordinate positions using an image sensing system having one or a plurality of optical systems. A plurality of depth information are extracted from image sensing related information sensed by the camera at the plurality of coordinate positions, and the plurality of extracted depth information are converted and unified into depth information expressed by a unified coordinate system.
What is needed is a way to read a barcode to identify an item from a video image of the item, and to then use the video image, with one or more additional video images, to determine the positions of additional features of the item, with the location of the barcode on the video images being further used to determine whether the locations of additional features match a permissible range of such locations for the item identified by the barcode.